My well water could be bottled, but the electric elements build up huge deposits of calcium that hinder their operation unless they break off and drop to the bottom of the standard tank unit. Which they do if using a HIGH watt density element.
If I had a tankless, I would spend hours a year filling it with lime away and trying to get a brush throught it to remove the lining that makes the efficiency about 1/2 of advertised.
tankless are foolish when the best is a $200 tank that has only 2 or three parts and sit on every shelf in America. Many life cycle cost tests prove it.
Sediment filters dont help with dissolved solids which tankless units like to extract.